Optimum Operating Pressure Ratio for Scroll Compressor

A scroll compressor has a bu~lt-in pressure ra~~o related to geometry of scroll wraps and efflciency of the compressor depends on the relation between the ratio and an operat~ng pressure rat~o. Th~s paper analyses theoretl.cal performance of the compressor by tak1ng account of flow resistances at opem.ngs of scroll wraps and leakage flows through wrap clearances. The flow resl.stance at the d1scharge opening causes an overcompression loss at a built-ln pressure ratio operation but lt reduces an undercompress1on loss at a high pressure rat~o operaclon, which leads an optlmurn operat~ng pressure ratio higher than the built-in pressure rat~o. Leakages accelerat.e pressure rl$@ durl.ng a compressl..on process and t"educes the compressor eff~clency more at a higher pressure ratio operat1on. Ps, Pd: r ra = T Tad' t v vo vc vn,vl Vs,Vd: ws,wd: a Oa Or ' Ep : nad: 8 ed K Os .p ~s· 1>e' w flow areas of suct~on and discharge openings flow area of discharge port basic circle radius th1ckness of wrap flow coeff~c~ent discharge port diameter he~ght of wrap average compress1on power lengths of tangent lines from po~nts on 1nner and outer curves sealing line length of tlp leakage mass of gas ln pocket mass flow rate effective suction mass flow rate rotat1onal speed of shaft pressure of gas in pocket suct1on and dlscharge pressure rad1us of revolut1on rad~us of start1ng c~rcular arc torque of crank shaft adiabat1c compress~on torque time volume of pocket volume of dlscharge pocket (V00 ,v01 :dlvlded d1scharge pocket volumes) clearance volume volumes ot suctlon and comp~ession pockets theoret1ca1 suct1on and discharge volumes Wldths of suct1on and discharge open1ng 1nvolu~e anqle correspond1ng to half of wrap thickness t1p clearance between wrap t1p and base plate flank clearance between wrap walls bu1lt~1n pressure rat1o ad1aba~1c compress1on efflclency ro~a~1onal an~l~ rotatlonal angle at discharge starting ad~abat1c compress~on exponent dens~ty of suctlon gas tnvolute angle 1.nvolu.t.e 5tartlng and ~nding angles angular veloc1ty of rotatlon